1. Field of Invention
The present invention relates to liquid crystal display devices and electronic apparatuses. More particularly, the invention relates to a liquid crystal display device using a multi-featured reflection film having low heat resistance.
2. Description of Related Art
Reflective liquid crystal display devices consume low power because they do not utilize light sources, such as backlights, for example. Therefore, reflective liquid crystal display devices have been widely used as display sections attached to various mobile electronic devices and apparatuses. Recently, it has been proposed to use new reflection films as the reflection layers for such reflective liquid crystal display devices, and examples thereof are dielectric reflection films in which dielectric thin films having different refractive indices are alternately laminated, cholesteric reflection films using cholesteric liquid crystals, and holographic reflection films. Since these reflection films can achieve display with higher brightness and higher color purity compared to the related art reflection films formed of metal thin films, they receive attention as techniques capable of enhancing display quality of liquid crystal display devices.
However, the newly proposed reflection films have lower heat resistance compared to the related art metal reflection films formed of Al, Ag, or the like. Therefore, in particular, when the reflection films are applied to active matrix liquid crystal display devices, characteristics of the reflection layers may be changed or degraded by heating in the process of forming TFTs (Thin Film Transistors) or TFDs (Thin Film Diodes). Such degradation of the reflection layers results in a decrease in display quality and a decrease in the production yield, thus presenting an obstacle to the application of the reflection films to active matrix liquid crystal display devices.
The present invention addresses the problems described above, and provides a liquid crystal display device which includes switching elements and a reflection layer having low heat resistance, and which can reduce or prevent the characteristics of the reflection layer from degrading due to heating in the manufacturing process.
The present invention also provides an electronic apparatus including the liquid crystal display device described above.
In order to address or solve the problems described above, the present invention provides liquid crystal display devices having the construction described below.
In one aspect of the present invention, a liquid crystal display device includes a pair of opposing substrates sandwiching a liquid crystal, a reflection layer disposed on one of the substrates, and switching elements disposed on the liquid crystal side of the other substrate. The switching elements drive the liquid crystal. The reflection layer is formed of a dielectric reflection film.
In another aspect of the present invention, a liquid crystal display device includes a pair of opposing substrates sandwiching a liquid crystal, a reflection layer disposed on one of the substrates, and switching elements disposed on the liquid crystal side of the other substrate. The switching elements drive the liquid crystal. The reflection layer is formed of a cholesteric reflection film.
In another aspect of the present invention, a liquid crystal display device includes a pair of opposing substrates sandwiching a liquid crystal, a reflection layer disposed on one of the substrates, and switching elements disposed on the liquid crystal side of the other substrate. The switching elements drive the liquid crystal. The reflection layer is formed of a holographic reflection film.
In the three modes of liquid crystal display devices described above according to the present invention, the reflection layer is formed of any one of the dielectric reflection film, the cholesteric reflection film, and the holographic reflection film having lower heat resistance compared to the conventional metal reflection film on a substrate (counter substrate) other than the substrate provided with the switching elements to drive the liquid crystal. That is, since the reflection layer is not disposed on the substrate provided with the switching elements which is heated at high temperatures in the manufacturing process, the reflection layer is prevented from being overheated or overheating is reduced, and thus the characteristics of the reflection layer are prevented from being changed or degraded or the changing or degradation of these characteristics is reduced.
With respect to the manufacturing process of the switching elements, if the switching elements and the reflection layer are formed on the same substrate, in order to manufacture the switching elements without degrading the characteristics of the reflection layer, the heating temperature during the formation of the switching elements must be decreased to the heat resistance temperature or less of the reflection layer. It is very difficult to manufacture the switching elements by decreasing the heating temperature to such an extent as described above, and the yield may be decreased because of the decrease in the performance of the switching elements. However, in accordance with the construction described above, the switching elements can be formed at ordinary processing temperatures, and a decrease in the yield can be reduced or prevented with respect to the substrate provided with the switching elements.
In the liquid crystal display device of the present invention, the switching elements may be TFDs. In the liquid crystal display device of the present invention, since the reflection layer and the TFDs are formed on separate substrates, the characteristics of the reflection layer are not degraded by heating when the TFDs are formed, and the heating temperature is not restricted by the heat resistance temperature of the reflection layer. Therefore, it is possible to form the TFDs by the related art manufacturing process. Consequently, it is possible to obtain liquid crystal display devices with high brightness and high color purity without decreasing the production yield.
In this construction, the substrate provided with the TFDs is placed on the user side, and since the wiring region in the substrate for TFDs can be decreased compared to the substrate for TFTs, the aperture ratio of pixels can be increased, and thus it is possible to obtain a liquid crystal display device in which a display with higher brightness is achieved.
Alternatively, in the liquid crystal display device of the present invention, the switching elements may be TFTs. In the manufacturing process of TFTs which requires a larger number of steps, since the heating temperature in the manufacturing process is also not restricted by the heat resistance temperature of the reflection layer, it is possible to employ the related art manufacturing process, and active matrix liquid crystal display devices can be produced with high yield.
In another aspect of the present invention, an electronic apparatus includes any one of the liquid crystal display devices described above. In the electronic apparatus having the construction described above, since the liquid crystal display device which can perform a display with high brightness and high definition is provided on the display section, visibility in the display section can be significantly enhanced.